Previously `report_fatal_error` is used for reporting something goes
wrong in the backend, but this is confusing because `report_fatal_error`
basically means there are something unexpected & crashed in the backend.

So, turn this "crash" into an elegant error reporting.
After this patch, clang can diagnose it:

    bpf-crash.c:4:30: error: Invalid usage of the XADD return value
        4 | u32 next_event_id() { return __sync_fetch_and_add(&GLOBAL_EVENT_ID, 1); }
        |                              ^
    1 error generated.

This PR is to address the issue #84640

This saves an extra iteration over the all instructions of the function.

This is a pure optimization to avoid redundant extensions, but iterating
over all users is expensive, so don't do this at -O0.

At the moment, Clang is rather liberal in assuming that 0 (and by extension unqualified) is always a safe default. This does not work for targets that actually use a different value for the default / generic AS (for example, the SPIRV that obtains from HIPSPV or SYCL). This patch is a first, fairly safe step towards trying to clear things up by querying a modules' default AS from the target, rather than assuming it's 0, alongside fixing a few places where things break / we encode the 0 == DefaultAS assumption. A bunch of existing tests are extended to check for non-zero default AS usage.

Issue #92687

This reverts commit 112eadd5.

Memory leak: https://lab.llvm.org/buildbot/#/builders/5/builds/43403

Issue #92687

This reverts commit 0ec3b972.

Revert "[Bounds-Safety] Temporarily relax a `counted_by` attribute restriction on flexible array members"

Together with 0ec3b972
breaks https://lab.llvm.org/buildbot/#/builders/5/builds/43403

Issue #92687

This reverts commit cef6387e.

No need for this to be vector specific, and its more likely that scalar cases will appear after #92576

No need for this to be vector specific, and its more likely that scalar cases will appear after #92096

[DAG] canCreateUndefOrPoison - only compute extract/index vector elt index knownbits when not poison

We were calling computeKnownBits to determine the bounds of the element index without ensuring that it wasn't poison, meaning if we did freeze the index, isGuaranteedNotToBeUndefOrPoison would then fail as we can't call computeKnownBits through FREEZE for potentially poison values.

Fixes #92569

Fixes build after cfe9deb1 on
https://lab.llvm.org/buildbot/#/builders/37/builds/34828

The only difference is the operand index for the element index variable.

This patch supports `G_CONSTANT_FOLD_BARRIER` on RISCV to generate the
following inst seq without crash:
```
define i64 @xor_and_i64(i64 %x) {
entry:
  %y = and i64 %x, 16383
  %z = xor i64 %y, 16368
  ret i64 %z
}
```

In order to test SelectionDAG for target AMDGPU, we need
CodeGenPassBuilder.

`__sanitizer_siginfo` has been introduced in D142117.
(llvmorg-16-init-17950-ged9ef9b4)
It is incompatible to -pedantic.

`clang_rt.ctx_profile` has been introduced in #92456.

The smaller class member are more focused and easier to maintain. This
also paves the way for partial header forward compatibility in
https://github.com/llvm/llvm-project/pull/88212



---------

Co-authored-by: Kazu Hirata <kazu@google.com>

Add 'sort' here since it's helpful when container type
changes (for example, https://github.com/llvm/llvm-project/pull/88024
wants to change container type from `unordered_set` to `DenseMap)

@MaskRay points out `std::` doesn't randomize the iteration order of
`unordered_{set,map}`, and the iteration order for single build is
deterministic.

Labels are matched using a regexp of the form '^(pattern):', which
requires the addition of a "suffix" concept to NamelessValue.

Aside from that, the key challenge is that block labels are values, and
we typically capture values including the prefix '%'. However, when
labels appear at the start of a basic block, the prefix '%' is not
included, so we must capture block label values *without* the prefix
'%'.

We don't know ahead of time whether an IR value is a label or not. In
most cases, they are prefixed by the word "label" (their type), but this
isn't the case in phi nodes. We solve this issue by leveraging the
two-phase nature of variable generalization: the first pass finds all
occurences of a variable and determines whether the '%' prefix can be
included or not. The second pass does the actual substitution.

This change also unifies the generalization path for assembly with that
for IR and analysis, in the hope that any future changes avoid diverging
those cases future.

I also considered the alternative of trying to detect the phi node case
using more regular expression special cases but ultimately decided
against that because it seemed more fragile, and perhaps the approach of
keeping a tentative prefix that may later be discarded could also be
eventually applied to some metadata and attribute cases.

Note that an early version of this change was reviewed as
https://reviews.llvm.org/D142452, before version numbers were
introduced. This is a substantially updated version of that change.

This will help in later patches where the checks for operands being
instructions is removed, and might help not remove unnecessary poison lanes.

As a small addition to #91148, this uses copysign to produce the correct
sign for zero when converting frem to div/trunc/mul when we do not know
that the input is positive (and we care about sign bits). The copysign
lets us get the sign of zero correct.

In testing, the only case this produced different results than fmod was:
frem -inf, 4.0 -> nan vs -nan

Fixes: 060df78c

The last use of the function has been removed a while ago. Remove the
unused function.

Add support for generating `st.param` instructions with direct use of
immediates. This eliminates the need for a `mov` instruction prior to
the `st.param` resulting in more concise emitted PTX.

Turns out it was already in Analysis/CFGLoopInfo, so just move it
to IR/AsmPrinter.

```
%1:gr64 = COPY $eflags
OP1 may update eflags
$eflags = COPY %1
OP2 may use eflags
```

To use eflags as input at 4th instruction, we need to use SETcc to
preserve the eflags before 2, and update the source condition of OP2
according to value in GPR %1.

In this patch, we support CCMP/CTEST as OP2.

Ignore `ImplicitCastExpr` when building `AttrExp` for capability
attribute diagnostics.

Fixes: https://github.com/llvm/llvm-project/issues/92118.

```
.irp foo,1
nop
.endr
nop
```

expands to an excess EOL between two nop lines. Other loop directives
and .macro have the same issue.

`Lex()` at "Jump to the macro instantiation and prime the lexer"
requires that there is one single \n token in CurTok. Therefore, we
cannot consume the trailing \n when parsing the macro(-like) body.
(commit c6e787f7 (reverted by
1e5f29af))

Instead, skip the potential \n after jumpToLoc at handleMacroExit.